Currency is one of essential elements for a circulation market. In order to ensure the stabilization of financial circulation sequences, currency authenticity identification is required.
During the process of printing, a plurality of magnetic codes will be configured and distributed on the currency. Currency authenticity identification is just conducted through identifying the characteristics of these magnetic codes. In the prior art, there are two categories for detecting the characteristics of the magnetic code, i.e., magnetic detection and optical property detection.
Magnetic authentic identification has been widely applied to currency detection due to its advantages as convenient detection and rapid computer detection, and the like. At present, financial magnetic authentic identification has become one of indispensable ways for maintaining the stabilization of the financial circulation sequence.
The principle of the magnetic authentic identification is to detect a magnetic code set in the currency, including such characteristics as the strength and position distribution of a magnetic field and the like. With the progress of technology, the financial magnetic authentic identification technology has been developed into a relatively advanced Hall magnetoresistance from an induction coil which is over-sensitive to banknote detection speed and detection interval. However, the Hall magnetoresistance has an extremely low reluctivity in a weak magnetic field; moreover, its identification procedure depends on the signal intensity of the magnetic code; therefore, an extremely small detection gap is required, which is usually less than 0.1 mm. Therefore, signals are instable due to gap change and other factors that affect the signal intensity, which are easy to cause a series of problems like high seizing-up rate and high wear rate of banknotes and easy fracture of a banknote pressing wheel due to high pressure.
And as shown in FIG. 1, it is impossible for the Hall magnetoresistance to simply and easily distinguish soft magnetism and hard magnetism due to its symmetrical responses to magnetic field directions, and it is more impossible for the Hall magnetoresistance to identify the entire magnetic hysteresis loop characteristics. It can only judge according to the geometrical and mechanical properties of the magnetic code unilaterally and try to use the signal intensity modulus or ratio of signals of different magnetic code, which causes strong dependency on the factors that affect the signal intensity of the magnetic code and indeterminacy to the judgment of the signal intensity; therefore, it is incompetent to implement thorough anti-counterfeiting through completely identifying the magnetism characteristics of the magnetic code. Facts proved that the Hall magnetoresistance cannot identity new-edition counterfeit banknotes appeared in recent years.
Moreover, the Hall magnetoresistance prevailing the market at present cannot avoid superposition of adjacent signals with small intervals, which causes complication of an identification procedure.
Today when science and technology are highly developed at present, it is not difficult to forge the magnetic field and position distribution of a true magnetic code. In addition, the foregoing indeterminacy during judgment using the conventional technologies brings challenges to authentic identification on the magnetic code.
Therefore, it needs to provide an authentic identification technology that can identify more technical characteristics of the currency. But actually, it is really very difficult to completely forge all the magnetic hysteresis loop characteristics of a plurality of true magnetic codes unless knowing the magnetic code formulation and manufacturing process of the banknote printing factories. Therefore, complete authentic identification cannot simply depend on comparing the magnetic fields and position distribution of the magnetic code, but also needs to be capable of qualitatively and quantitatively identifying the soft and hard magnetism attributes of the magnetic code and the magnetic hysteresis loop characteristics, so as to ensure the stability for signal judgment and reduce the indeterminacy of the identification method.
Therefore, it is very necessary to provide a magnetic sensor and a method for quantitatively identifying magnetic hysteresis loop characteristics of magnetic code with respect to the defects of the prior art.